1. Field of the Invention
The invention relates to an image display technique, and more particularly to an image display having resolution conversion.
2. Description of the Related Art
This application claims the benefit of U.S. application Ser. No. 12/340,792 entitled “Image Resolution Adjustment Method” filed on Dec. 22, 2008. The disclosure of the Application is incorporated herein.
For current display devices, electronic monitor systems are widely applied in various applications, such as digital cameras, liquid crystal display (LCD) devices, and LCD televisions. In order to conform to specifications of electronic monitor systems with different resolutions, the resolutions of image sources have to be controlled by scaling images. For example, when a resolution of an input image is in VGA mode (640×480) while an output device is in XGA mode (1024×768), the resolution of the input image has to be enhanced, and when a resolution of an input image is in SXGA mode (1280×1024) while an output device is in XGA mode (1024×768), the resolution of the input image is degraded.
Conventional image scaling control techniques usually use resolution (i.e. pixel or line of an image) interpolation or replication during an image upscaling period. An image which is upscaled by interpolation advantageously has smooth edges from the perspective of human vision; however, the content of the original image is changed so as to result in image degration for its accuracy. When an image is upscaled by replication, disadvantageously, the image has sawtooth edges if the scaling ratio for the image is not controlled appropriately, resulting in degraded quality of the image.
Please referred to FIG. 1, U.S. Pat. No. 6,587,602 discloses a resolution conversion system. The system mainly includes a horizontal scaling calculation section 101 and vertical scaling calculation section 102, wherein the horizontal scaling calculation section 101 receives original image data 103 of 8 pixels constituting one single horizontal line and another original image data 104 of 8 pixels constituting a subsequent single horizontal line, and converts the number of pixels in a horizontal direction. In addition, the horizontal scaling calculation section 101 is supplied with a control signal 108 representative of a horizontal magnification factor for indicating how many pixels are to be added to the pixels of the original image in the horizontal direction. The vertical scaling calculation section 102 receives image data 105 of 8.±.n pixels constituting the line output by the horizontal scaling calculation section 101 and another image data 106 of 8.+−.n pixels constituting the next line output by the horizontal scaling calculation section 101. In addition, the vertical scaling calculation section 102 is supplied with a control signal 109 representative of a vertical magnification factor for indicating how many pixels are to be added to the pixels of the original image in the vertical direction. The vertical scaling calculation section 102 executes the above mentioned process successively for the original image data of the pixel block unit of 8.times.8 pixels, whereby the image data 107 of a line to be interpolated are generated so as to convert the number of pixels in the vertical direction. However, the prior art uses interpolation to provide the resolution conversion so as to cause original pixel data change from the source image unfortunately, and it is not appropriate in some cases of the emergent medical surgery because this situation does not allow any change of original pixel data to prevent any of the medical mistakes from viewing the original medical images.
Besides, U.S. Pat. No. 7,199,837 also discloses a system for improving a ratiometric expansion. The prior art provides, after an image being enlarged by a replicator, the resolution of the image re-adjusted by a re-sampler. However, the prior art is trouble with disadvantageously complicating image scaling calculation and smoothness.